1. Field of the Invention
This invention relates to a transition metal organometallic compound comprising a transition metal in any one of group 3 to group 10 of the periodic table and cyclic compounds containing a heteroatom in group 15 or of the periodic table and having a cyclic structure including a .pi.-bonded portion and composed of the heteroatom and the .pi.-bonded portion, wherein the transition metal has a bond of a .pi.-bonding heterocyclic ligand, the heteroatom and the .pi.-bonded portion, relates to a catalyst system using the foregoing transition metal organometallic compound as a main catalyst and using solely an organometallic compound, aluminoxane or ionized ionic compound or their combinations as a co-catalyst, and relates to a method of polymerizing olefin in the presence of the foregoing catalyst.
2. Description of the Related Art
A variety of polymerization methods and catalyzer systems have been known for use to polymerize olefin. It has been known that a conventional Ziegler-Natta catalyst composed of a transition metal compound using alkyl aluminum as a co-catalyst is able to manufacture Polyolefin that exhibits a wide distribution of molecular weight.
Recently, a catalyst system including a transition metal compound (generally called a "metallocene compound") that contains a cyclopentadienyl derivative as a ligand has been developed. The foregoing catalyst system serves as a polymerizing catalyst for olefin, and, in particular, metallocene composed of group IVA transition metal such as titanium, zirconium or hafnium has been used to manufacture polyethylene, ethylene copolymer or polypropylene or the like. It has been found that use of aluminoxane as a co-catalyst enables polyolefin to be manufactured actively (for example, see Japanese Patent Laid-Open No. 58-19309).
A multiplicity of investigations have been made and results have been reported about catalyst systems of the type containing a group IVA metallocene compound and aluminoxane, the group IVA metallocene compound having a variety of cyclopentadienyl derivatives. As a result, it has been found that introduction of a variety of substituents into the cyclopentadienyl group enables the stereostructure of generated polymer, the primary structure such as the composition distribution and the manufacturing efficiency to be controlled (for example, see Japanese Patent Laid-Open No. 61-26491, Japanese Patent Laid-Open No. 64-51408, Japanese Patent Laid-Open No. 64-66216, Japanese Patent Laid-Open No. 1-301704 and J. Am. Chem. Soc. 1988, 110, 6255-62 and so forth).
Since a necessity of using a large quantity of aluminoxane raises an industrial problem, investigations have been undertaken to use a variety of organic metal compounds to serve as a co-catalyst in place of aluminoxane (for example, see Japanese Patent Laid-Open No. 3-197513, Japanese Patent Laid-Open No. 3-290408 and so forth) and investigations of polymerization of olefin using cationic metallocene compound (for example, see Japanese Patent Laid-Open No. 3-207704 and so forth) have been undertaken.
According to the foregoing specifications, polymer obtainable from the polymerization using the metallocene compound exhibits several characteristics that the quantity of oligomer that raises a problem in terms of performing a process is small and that a uniform composition distribution is attained when it is used to manufacture polypropylene or ethylene-.alpha.-olefin copolymer. However, its narrow molecular weight distribution raises problems in terms of the processability and mechanical strength. Although a variety of investigations have been undertaken to overcome the foregoing problems, a satisfactory result has not been obtained yet. Accordingly, there arises a necessity of developing a novel catalyst system that is able to overcome the foregoing problems.